filling radiator, triggering thermostat valve

[Lope]

I gave my bike's cooling system some long overdue TLC. The coolant overflow bottle thing was so full of mold.

I pulled off the pipe that goes from the radiator to the engine block on the left side, hooked it up to a garden the hose pipe... the brownest dodgiest smelling shit ever came out of the bike, and I let it run for a while, pushing the water through in both directions, also forcing the crap out of the overflow pipes etc.
I took the overflow bottle thing off, and put about 100 washers in it with hot water and shook it like crazy, doing that and using and an old toothbrush sorted it out. (whats the point of the overflow tank anyways? why not just vent it to the ground? antifreeze caution?

I poured in some anti freeze and fresh water into the radiator, and filled it up to the top. I figured there must be air bubbles in the coolant loop, so I started the bike hoping it would cycle around, but the water level stayed the same. The engine was cold, so I figured it must be the thermostat valve.
Is there any way to trigger the thermostat valve artificially?

I figured once I get the water circulating through the loop, I'll top the radiator up full again?

Anyone tried those commercial coolant cleaner solutions? or vinegar?

what is that mini radiator? oil cooler? mine has 2 thick pipes going to it, and 2 20cm long thin pipes, which lead nowhere! hehe

[Cammo]

whats the point of the overflow tank anyways? why not just vent it to the ground? antifreeze caution?

It collects the overflow of water that expands when it gets heated. When the coolant cools back down, this goes back into your radiator. Good idea to keep it clean!

Is there any way to trigger the thermostat valve artificially?

You could take it out and put it in a pot on the stove, seeing at what temperature it opens

[Lope]

Clever idea for checking the thermostat valve.
So I've basically got to ride the bike and wait for it to get up to temperature, to see where the water levels are at?

Is it a good idea to open the water pump?